Ordinary water evaporators are notoriously expensive to operate since evaporating water requires large quantities of energy because of its high heat of vaporization. To evaporate large quantities of water a heat pump is often employed to efficiently recycle the heat of vaporization. One heat pump method is the mechanical vapor recompression process that when applied to the evaporation of water requires the direct compression of steam. The need for a rugged and simple steam compressor would greatly expand the use of mechanical vapor recompression for water evaporation. Other applications for a rugged and simple steam compressor might arise in any instance where the pressure of the steam available is too low for its intended purpose and must be upgraded by compression.